Method of forming composite mica sheets



March 29, .1927' MocARTHY METHOD OF FORMING COMPOSITE MICA SHEETS l' INVENTUM FYMQMQTQWMAWSL liatented Mar. 29, l UNITED sITATEIs PATENT olfllciz;

Louis MQGARTHY, oF BosToN; MAssAcHUsETTs, Asarcuw'oiv. To 'THE MAcALEN f COMPANY, orVBosToN, iiirAssAcmJsETTs', A CORPORATION or MASSACHUSETTS.

- METHOD F FORMIG OIPOSITE MICA 'SHEETS.

Application led November 6,1922. Serial No. 599,249.

Thisinvention relates to the manufacture ofthe tray so that the resultantsheets are of composite sheets from flaky or plate-like characterized by a lack of adequate adhesion material, and especially, although not exclu- .between the constituent plates -at these sively, to the production of the micadsheeuts points.

used in the manufacture 'of insulators, as, With a View to decreasing the time and 6o for example, insulating bushings, thimbles, labor involved in the manufacture of these etc. In making these and other4 articles Sheets, it has been proposedto shower theV from mica, asfalso in the use of mica for plates or flakes upon the trays, attempting lsome other purposes, it is necessary to em- 1n this way to spread them evenly, until l0 ploy sheets of .material of greater area, thickthey have been deposited thereonto a suf- 65 ness, cohesion and pli-ability than can be iicientdepth, and thereaftel tO'ttempt t0 `found in nature. -The natural -jlazninae of force the binder into the spaces 'between mica are of limited size and the masses therethem .und/e1" pressure `0l' by means 0f e of', of whatever thickness, tend to separate "aeuum 0I' Otherwise. Such attempts have l5 along their lines of cleavage int-,0 their C611- not been altogether successful, inasmuch as it 70 l stituent plates, flakes or laminae, so that a is ditiicult inthis way to cause the binder to sheet of mica, even if it can be obtained in penetrate' the sheet t0 e Slllieient extent to its natural` ,form 0f a, Sufficient area and glVe the Sllet tSIleCeSSary tenacity, the Sheets thickness, which is unusual, is not' sufficiently S0 formed being alsO S0 limited 'in size that the pliable, and has not sufficient cohesion along SHVlIlg II time and'labOr is small. Various 75 its lines of cleavage, to enable the same to Other IOPOSd methOdS 0f manufacturing be shaped or moldedJ in the desired manner. Such Sleets `in quantities lhave, for l.similar It has, therefore, been customary to build reasons, failed to accompllshthe desired reup composite sheets of considerable size from Sult 111 a Satlsfactory manner, by reason the natural plates 01: Hakes 0f fmica b eeeither of the tlme and skilled labor requlred 80 inenting them together with a suitable blnder t0 Practicey them 0I' 0f the defeetivequallty in liquid form, as for example' shellac. lSuch 0f the Sheets PIOdllCed-V f sh-eets can be rendered pliable by heat, vhich I hilVe'fOllIld 'that by ShOWeImg the Plates softens the shellacg' and can be cut,V d ieor flakes from a considerable helght, prefer- 0 shaped, or otherwise workedinto the desired .ably from a `foraminous container, such asa 85 articles. These composite'sheets have, for rotating "drum, upon a suitable egztended the most part, been madel by hand, usually substantially plane surface, spreading the t by girls who use a suitable -frame or tray liquid binderl upon the plates 0r akespn having -a bottomof wire gauze upon' which said surface as the showering operation sive layers with the` interposition, from binder will be caused to penetrate the intertime to time, of a suitable amount of shellac stices between the superimposed and lnterbinder, manually applied to the Hakes, this locked lates or flakes, and a sheet of subthe plates or flakes of mica are laid in succesprogresses, and olling the Whole, said uo operation being continued until a sheet of stantial constant thickness, great tenacity, j the desired thickness has been built up, the and uni orm dielectric property will be pro-` 95 rame' being held before or over a suitable duced. Also, by relatively moving the sur-A light for the assistance of the girl in keepvface and the drum or other container from ing the sheet of'an Aapproximately even which .the plates or flakes 'are showered, 'it thickness. This operation `is slow 'and will be seen thata sheet of an area limited pending largely upon the care and skill of amount ofrelativemovement may-be made. the individual operators, and it being prac- Such asheet may be produced at a very small tically .impossible to form 'a .sheet having fraction of thecost and in a very small fracstraight, square edges of the same even tion'of the time necessaryto produce-an equal the sheet. vThis is due tothe fact that the 1s of considerably better quality' than any binder is ap liedby hand tothe plates after material which can be produced by suchY they are lai in the tray, and this binder is methods. f not thoroughly `Worked intothe interstices The improved method above outlined,l

-5 laborious, thc quality of the product. deonly by the area of said surface' and the 1110 'i thicknessrand cohesion asfthe remainder ofy quantity by any of the present methods and l between the plates at the 'edge and corners which constitutes the presenty invention, will be best understood from the following description of the operation of the apparatus shown inthe accompanying drawings, 'by which it `may be practised. This apparatus isnot claimed herein, being covered by the claims of another application led of even date herewith, Serial No.l 599,248. And since I believe myself composite sheets of mica or similar material by showering the Vconstituent plates or flakes from an elevated source upon sreceiving surface, while relatively moving said 'source and surface, or while simultaneously supplying .a `liquid binder, I wish to claim my invention broadly and to have it understood that the particular apparatus and mode. of operation hereinafter described, as well as the particular materials referred 'to, have been chosen for illustrative purposes merely, and that the invention, as defined by the claims hereunto appended, ma be otherwise practised without departur rom its spirit and scope.

In said drawings: y Fig. 1 is a somewhat diagrammatic side elevation, partly broken out, of the substantially complete apparatus.

Fig. 2-is aplan view of the parts shown in Figure 1.` V

Fig.. 3 is an enlarged end elevation of the apparatus partly broken awaylooking from n the left in Figure 1.

- ports 16 'and at or the like, rin order-to re uce Fig. 4 isa detailtransverse section, on a further enlarged scale, of a portion of one ,A

edge of the ed and certain ofthe parts cooperating therewith.

The apparatus as a whole comprises an elongated bed 15 mounted on suitable su the -op osite sides of Whic i, and e tending longitudinally thereof, 'are rails 1 constituting .a track upon which is mounted to travel a carriage 18 having?y at opposite sideswheels 19 to run on said track, and carrying in elevated position means for showering micaor simi-lar plates or flakes upon the bed'l, the arrangement being such -that said carriage/'extends across the 'bed for ,the entire width ofthe gitudinally over the sameas run upon the track 17 The bed 15 is preferabl the wheels 19 composed of 'slate to afminimum the el'ect of expansiony and. contraction, and is formed along its o posite longitudinal edges with parallel vertlcal ribs 20 (see particularl"v Figure 4) for a purpose hereinafter explained. i Extending longitudinally 'over and 25 suitablyA the upper surface'of 'the bed 15, `and of a width substantially equal to' the distance between the ribs 20, is a belt or apron 21 of canvas .or other suitable fabric, said belt passing over transverse rollers 22 and 23 at the opposite ends of the bed, and havingA its vends secured to and wound upon drums 21 journalled beneath the bedto be the first to form latter and moveslonwhich the mica, indicated at m in Figure 3,

is showered. T he drum 24 is carried by a shaft 26 and may be operatively connected, through a clutch 27 beltl pulley 28 adapted to receive power from any suitable source through a belt 29. The particular vclutch mechanism herein shown is of the well-known type usually employed .for controlling the drums of donkey hoists.

The drum 25 is geared to an electric motor 31 Acontrolled by a switch (not shown) locatedfat an convenient oint-.. The end 21a (Fig. 2) o the belt 2l,w ich is connected with the drum 25, is of reduced width, as shown in Figure( 3, in order to reduce the tendency7 of said belt to stick to the bed 15 when moved longitudinally thereover, while `the roller 23 at that end of the bed is somewhat crowned, thereby drawing the belt taut vat its longitudinal center andcausing the same to lie flat upon the bed 15.

The carriage 18 is propelled along the track 17 and over the bed 15 by means of an electric motor 32 which receives its power from a generator or other source 33 (Fig. 2)- through conductors 34 extending parallel to the track and engaged by a shoe 35 carried by an arm 36 on said carriage. The electric circuits and connections'between the contact faces on the shoe l35 and the motor 32 are not shown in detail herein, as they may be of any well known character, said connections. however. including a main switch or controller 37 (Fig. on the side of the carriage, and a reversing switch 38 (Fig. 3) associated'with the'motor 32. The reversing switch 38 is operated to reverse the direction of travel of the carriage by means of a link (Figs. 1 and 3) connected with an arm 71 on a rock shaft 72 journalled in the carriage and having a handle 39 co-operating with pivoted, spring-pressed stops or trip devices 4() located atY opposite ends of the machine, whereby the travel of said carriage is automatically reversed when said carriage reaches eitherend of the bed 15.

ofv a hopper carrying at its upper end one or more rotatable, forammous drums 41.

'As herein sho-\vn,..three drums l1 are em ployed. said drums-being mounted in bearings 42 inthe upper parts of/the side walls of thefcarriage 18 and being connected by gears Llf3-with each other and by a lgear 41 ywith another electric motor 45 on the car-- riage, the motor 45 being connected in multiple with the .motor 32 between the main switch 37 and the reversing switch 38, so thatthe rotation of the motor 45 will be vcontinuous in onedirectiolr irrespective. of the reversal ofthe motor 32, it having been fou-nd that better results are obtained by rotating the drums 41 constantly in -the same direction irrespective ofthe direction by a handle 30, with a llt) YThe body of the carriage 18 is in the form of travel of the carriage 18. The drums 41 l are preferably composed of -woven wire as hereinafter explain fabric of relatively large e 9 an eccentric weight 47 so arranged. that whenV the motr 45 is stopped said drums will be.

Q brought to 'rest withy their 'covers 46 at the top'for convenience in filling through the A plates fall top of the hoppeluV VSaid hopper is prefer ably formed 'with one or more suitably located 1windows 48 through l which the showering of material from the drums may be observed. The walls of the hop er enclose the space through'which the p ates or flakes of mica m fall upon the bed and there fore shield the falling plates'or atmospheric disturbance in the Workroom. It is portance, in securing an even spreading of the materialen the bed, that the Hakes or through a substantially still atmos` phere. f Y

At each end of the carriage 18, and supported by larms 49, is a roller 50 ada ted to The material is through a pipe or co-operate with the. bed 15 and-the elt 21 thereon, as the carriage moves thereover, to r'oll down the material on said belt.' As shown most clearly lin Figure 4, the arms 49 are made as thin as to the s binder in liquid form, as for example analcohol solution of shellac. Each of the tanks l51 communicates through a nozzle 52 controlled by a manuwith ay strainen or filter 54, the latter in turn communicating pipes 55, with a perforated s rinkler pipe 56' extending transversely dtp the carriage immediately over the correspondingr roller 5.0 so as to discharge thereupon. By providing rollers 50 andv tanks` 51 at both ends plates or flakes onthe bed are supplied with a of the carriage, the

binder` and are'rolled down clear to the ends of the bed irrespective to produce composite sheets ofconsta-'nt thickness and tenacity throughout and with straight', square, i l

showered and the binder spread over the full width of,l the bed bctween the ribs, and the compressivel action l*of the rollerstends to force l`the binder into the angles between the ribs and Athesurface of the bed, thereby resulting in fully as great an adhesion'between the vconstitutent plates at the edge of the sheet as in any part there- Anyportions of the plates or. flakes4 which may fall against and vtend to project l' roller 22 is located flakes fromL caused by drafts' found to be of immica or other practicable, so that the .rollers 50 are substantially equal in width ace between the ribs 20. Also cari ried at either end ofthe carriage 18 is a tank or reservoir 51 for a suitable the pla-tes or"flakes in of the length of the carriage. The ribs .2O and roller 50 cooperate.y

ment' of theN operator, abrupt, and parallel edges.

@binderto be sprinkled u broken oft' thereagainst by the lends of the rollers, thereby producing straight edges on the sheet. v j At the lend .of the bed A15 adjacentthe a pairof shears of any standard and suitable type'comprising fixed 'and movable knives 60 and 61. from said end of the machine are suitable supports 64 upon which,and anotherlsuit# -able supportin the 'form of a ledge 65 ad- 'acent the fixed knifeGO ofthe sliearsinay e placed trays 62 to" receive the finished product. with foraminous bottoms ample,` of woven wire fabric,ito facilitate the drying of the composite.4 sheets. The supports 64prefera'bly carry at their upper yedges positioning pins 63 which extend through the fabric` ofV the bottoms of the trays 62 for a purpose hereinafter explained.

In carrying out my improved method by means of the apparatus above described, the plates or flakes are preferably first gradedaccording to size, as for example, by being passed through a suitable scf. ries of screens,l and flakes of approximately equal size'placed in the ldrums 41 through thedoors 46 therein,

the mesh` of.the fabric forming said drums' being preferably chosen in accordance with the Vsize or grade ofl material tov be used thereinf The motor 31 and drum 25 Yare operated to-draw the belt 21 substantially as far as possible toward the left. as shown in Figure 2, and the `main switch 37 operated to start the motors 32 and 45. The carriage 18 will thereupon travel longitudinally of the bed and the .rotating drums 41 will shower the plates lor flakes upon said bed, substantially covering the same, said flakes beyond the `ribs .are bent upwardly' and` a supply of plates or Spaced i Said trays are preferably formed composed,l for ex' or plates being rolled down by the rollers 50 as the carriage passes` thereover. The direction `of travel of the carriage is automatically reversed, as above explained, from time to time,'as each longitudinal traverse of the bed is completed, thereby evenly depositing ing roller 50 and by it applied to and evenly spread upon the flakes or plates below it, said roller at the same time 'rolling and compressing thev whole;l Said binder pene'- .trates the interstices between ,the severalv plates or 'flakes lsoas to 'unite the same into a solid sheet which is compacted and made,- of even thickness rollers 50, said pressure also assisting '-inpon the correspond-` by. the pressure ofthe successive layers, the

forcing the binder througjghout the material. Where three drums 41 are employed, as in the construction shown, one or the other of the valves53 will usually be leftopen to a greater' or less extent throughout the operation, With the exception of the first traverse of the carriage which lays the first layer of plates or flakes upon the belt.v In some drums 41 is used, or

however, as-when a fewer number of cases,

if a sprinkler of greater J capacity be employed, it may be found suffivalves open three long;-

lably greater cohesion between the several laminare, and one which is of a more pliableI character. The operations aboveidescribed are successively repeated by successive trips of the carriage 18 until the sheet S (Fig. 4), built up upon the belt 21, is of the desired thickness. whereupon the switch 37 is operated to stop the carriage, preferably when the latter-is at the end of the bed vopposite the shears, as shown in Figure 1. The

' clutch 27 is then operated by the handle 30 position farthest to the to cause the drum 211 to draw the` belt 21 toward ,the right, as viewed in Figures 1 and 2, and over the roller 2 2, this abrupt bending of the belt causing the sheet S to leave the same and to be fed over the fixed knife and-upon the tray 62, until its .forward end or edge 1s brought into contact with the stop plns 63. The clutch 27 1s then released and the knife 61 operated to cutoff a section of the sheet, thev tray 62 p removed, another onevput in its place, and the operations repeated until the entire sheet S has been cut up into sections of convenient size. The. belt 21. being then drawn into the right, as viewed in Figures -1 and 2, the drum 25 is again operated bv the motor 31 to rewind sai belt, and the mechanism is in condition to commence the formation of another sheet.

It is found in practice that, by the elnplov'ment of the improved methodabove` described, two or three menA can. in a given ti1ne.- produce as great a 'quantity of composite sheets as can two hundred or. more operators by the old hand method, and that the -sheet .so .produced is of a more even and better quality .than the material producedv by said former' method'.

At all events",

. face. spreading a adding a binder in the whole upon said 2. Theherein described method of mak-- ing composite sheets which includes showering successive vated source fupon a suitable surface andl spreading a binder in liquid form over each layer and rolling the same upon said surface prior tol the deposit of the next succeeding layer.

surface and, as the' layers of flakes from an ele- 3. The hereindescnbed method of making composite sheets which consists in showering the constftuent flakes from an elevated source upon a` suitable surface while relatively and progressively m'oving said source and surface alternately in opposite directions, and as the showering -`rprogresses, adding a'y binder in liquid form wjllile rolling the whole upon said surface. g

4. The herein described method 'of making composite sheets which consistsi-n showering the constituent flakes from an elevated source upon a surface while relatively and progressively movingsa'd source 'and surface until said flakes have been deposited over the desired,area of said surface, adding a binder to vthe flakes on said surface, rolling the whole upon 'said surface, and successively repeating the flakes have been deposited to build up a sheet of the desired thickness. f

5. The herein described method of making composite. sheets which consists in showering the constituent flakes from one or more elevated, rotating foraminous drums while progressively moving said drum or drums over said surface until said flakes have been deposited over thedesired area of said surbinder in liquid form over the flakes .deposited and simultaneously rolling said plates and binder upon said surface, and successivelyv repeating the foregoing d operations until a sheet of theJ desired/thickness has been built up.

6. The herein described method of making composite sheets which consists in showering the constituent flakes from an elevated source upon a substantially plane. surface, adding a binder in liquid form to the flakes upon said surface as the progresses, and simultaneously rolling kthe Same.

vIn testimony whereof I affix iny signature.

LOUIS MGCARTHY.

foregoing operations until a sufficient number of layers of sa1d plates or showering operation 

